Continuous cooling capacity regulation using supplemental heating

ABSTRACT

A method of providing variable cooling includes operating a cooling element to cool an air flow by a first cooling capacity, operating a heating element to heat the air flow by a first heating capacity that adjusts the first cooling capacity towards a first desired total cooling capacity, determining a second desired total cooling capacity, controlling the cooling element to cool the air flow by a second cooling capacity that is greater than the second desired total cooling capacity, and controlling the heating element to heat the air flow by a second heating capacity that adjusts the second cooling capacity towards the second desired total cooling capacity. Further embodiments and cooling systems are also disclosed.

BACKGROUND OF INVENTION

1. Field of Invention

Embodiments of the invention relate generally to devices and methods for cooling electronic equipment. Specifically, aspects of the invention relate to methods of providing variable cooling capacity to electronic equipment by supplementing a cooling device with a heating device.

2. Discussion of Related Art

Heat produced by electronic equipment can have adverse effects on the performance, reliability and useful life of the equipment. Over the years as electronic equipment becomes faster, smaller, and more power consuming, such equipment also produces more heat, making control of heat more critical to reliable operation.

A typical environment where heat control may be critical includes a data center containing racks of electronic equipment, such as servers and CPUs. As demand for processing power has increased, data centers have increased in size so that a typical data center may now contain hundreds of such racks. Furthermore, as the size of electronic equipment has decreased, the amount of electronic equipment in each rack and power consumption of the equipment has increased. An exemplary industry standard rack is approximately six to six-and-a-half feet high, by about twenty-four inches wide, and about forty inches deep. Such a rack is commonly referred to as a “nineteen inch” rack, as defined by the Electronics Industries Association's EIA-310-D standard.

To address the heat generated by electronic equipment, such as the rack-mounted electronic equipment of a modern data center, air cooling devices have been used to provide a flow of cool air to the electronic equipment. In the data center environment, such cooling devices are typically referred to as computer room air conditioner (“CRAC”) units. These CRAC units generally intake warm air from the data center and output cooler air into the data center. The temperature of air taken in and output by such CRAC units may vary depending on the cooling needs and arrangement of a data center. In general, such CRAC units intake room temperature air at about 72° F. and discharge cooler air at below about 60° F.

The electronic equipment in a typical rack is cooled as the cool air is drawn into the rack and over the equipment. The air is heated by this process and exhausted out of the rack. Data centers may be arranged in various configurations depending on the purposes and needs of the data center. Some configurations include a room-oriented configuration in which cool air is output in general to the data center room. Other configurations include a row-oriented configuration in which CRAC units and equipment racks are arranged to produce hot and cold air aisles. Still other configurations include a rack-oriented configuration in which each rack has a dedicated CRAC unit.

A CRAC unit, as well as other typical cooling devices, may include an evaporator that cools air as the air flows over the evaporator's coils. Coolant flows within the evaporator's coils and evaporates as the coolant is warmed by the air passing through or over the coils. To re-cool the coolant, a cooling device may include a condenser. Cool air flows through or over the coils of the condenser causing warm coolant to cool and condense as it flows within the condenser's coils. A compressor may control the rate of coolant flow within the coils of the evaporator and the condenser so that as the compressor speed increases, the rate of coolant flow increases as well, resulting in more cooling of the air flowing through the CRAC unit.

Compressors may be limited in operation to a set of discrete speeds or a range of variable speeds that correspond to cooling capacities of the cooling device. Some compressors may be non-variable such that when the cooling device operates, the compressor provides only one cooling capacity (i.e., only one change in the heat of air passing through the cooling coils over a period of time). In some cooling devices, a matrix of such non-variable compressors may be combined to act as a semi-variable compressor. Such a matrix may provide discrete steps of cooling capacities corresponding to the numbers of compressors in operation.

Other compressors are semi-variable such that they provide a variable cooling capacity over a minimum threshold value, but do not operate below that threshold level. Operation of such variable compressors below the minimum threshold level may result in compressor failure due to motor burnout, burning of bearings, and/or overheating. Some compressors may be further limited in their variability to a limited number of compressor speed changes over a period of time.

SUMMARY OF INVENTION

One aspect of the invention includes a method of providing variable cooling. In one embodiment, the method comprises operating a cooling element to cool an air flow by a first cooling capacity, operating a heating element to heat the air flow by a first heating capacity that adjusts the first cooling capacity towards a first desired total cooling capacity, determining a second desired total cooling capacity, controlling the cooling element to cool the air flow by a second cooling capacity that is greater than the second desired total cooling capacity, and controlling the heating element to heat the air flow by a second heating capacity that adjusts the second cooling capacity towards the second desired total cooling capacity.

In one embodiment, cooling the air flow comprises cooling a first portion of the air flow, heating the air flow comprises heating a second portion of the air flow, and the method further comprises an act of combining the first portion and second portion. In some embodiments, the further comprises directing the air flow to at least one piece of electronic equipment. In one embodiment, directing the air flow comprises directing the air flow to a data center room containing the at least one piece of electronic equipment is stored. In one embodiment, directing the air flow comprises directing the air flow to an equipment rack containing the at least one piece of electronic equipment is stored.

In some embodiments, controlling the cooling element includes operating the cooling element at one of a set of discrete cooling capacities at which the cooling element is capable of operating. In one embodiment, controlling the cooling element includes adjusting the one of the set of discrete cooling capacities by heating the air flow. In one embodiment, the cooling element includes at least one compressor having a set of discrete compressor speeds, and controlling the cooling element includes selecting one of the discrete compressor speeds.

One aspect of the invention includes a cooling system. In some embodiments, the cooling system comprises a cooling element configured to cool a fluid flow by a variable cooling capacity to lower a temperature of the fluid flow, a heating element configured to heat the fluid flow by a variable heating capacity to raise the temperature of the fluid flow, and a controller configured to vary the cooling element and the heating element to generate a variable total cooling capacity corresponding to a combination of the variable cooling capacity and the variable heating capacity.

In some embodiments, the cooling element is configured to cool a first portion of the fluid flow, the heating element is configured to heat a second portion of the fluid flow, and the system further comprises a discharge configured to combine the first portion and the second portion. In some embodiments, the cooling element includes at least one compressor configured to move a coolant through a cooling coil at a coolant flow rate that corresponds to a cooling capacity of the cooling element. In one embodiment, the compressor is configured to operate at one of a set of discrete coolant flow rates at which the at least one compressor is configured to operate. In one embodiment, the compressor is configured to operate at a coolant flow rate above a minimum coolant flow rate. In one embodiment, the at least one compressor includes a plurality of compressors.

In some embodiments, the cooling system further comprises a discharge configured to direct the fluid flow to at least one piece of electronic equipment. In one embodiment, the discharge includes at least one fan. In one embodiment, the cooling element, heating element and discharge are part of a computer room air conditioning (CRAC) unit. In one embodiment, the heating element is disposed in the fluid flow between the cooling element and an object. In one embodiment, the cooling element is disposed in the fluid flow between the heating element and an object.

One aspect of the invention includes a method of providing variable cooling. In some embodiments, the method comprises determining a desired total cooling capacity of an air flow, adjusting a cooling device to produce a variable cooling capacity to the air flow that is at least as great as the desired total cooling capacity, and in a first mode of operation, if the variable cooling capacity is greater than the desired total cooling capacity, adjusting a heating device to lower the variable cooling capacity towards the desired total cooling capacity.

In some embodiments, the method further comprises directing the air flow to at least one piece of electronic equipment. In some embodiments, adjusting a cooling device to provide the variable cooling capacity includes adjusting at least one compressor speed of the cooling device. In some embodiments, adjusting a heating device to lower the variable cooling capacity towards the desired total cooling capacity includes adjusting a power supplied to a heat exchanger of the heating device. In some embodiments, the desired total cooling capacity includes a cooling capacity that reduces a temperature of the air flow to a target temperature and the variable cooling capacity includes a cooling capacity that reduces the temperature of the air flow to a predetermined temperature that is lower than the target temperature. In some embodiments, the first mode of operation includes when the predetermined temperature differs from the target temperature by at least a threshold amount. In some embodiments, the threshold amount includes about five degrees Fahrenheit.

The invention will be more fully understood after a review of the following figures, detailed description and claims.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:

FIG. 1 is a perspective view of a cooling unit of an embodiment of the invention;

FIG. 2 illustrates a schematic view of a heating element that may be used in an embodiment of the invention;

FIG. 3 illustrates a schematic view of a portion of a cooling unit of an embodiment of the invention;

FIGS. 4A-D are four views showing data center configurations with each data center configuration being cooled in accordance with an embodiment of the invention;

FIG. 5 is a diagram of components of a cooling unit of an embodiment of the invention;

FIG. 6 is a flow chart showing the control of a cooling device in accordance with one embodiment of the invention; and

FIGS. 7A-D are four graphs illustrating the output of a cooling device in accordance with embodiments of the invention.

DETAILED DESCRIPTION

This invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” “having,” “containing,” “involving,” and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

In accordance with one aspect of the invention, it is recognized that temperature fluctuations, as well as over-cooling and under-cooling may have an adverse effect on the performance, reliability, and useful life of electronic equipment. As described above, because a compressor of a typical cooling device is limited in its variability, typical cooling devices may over-cool, under-cool, and/or cool with a fluctuating temperature.

For example, for electronic equipment that has an optimal temperature at which it should be cooled, at a given air mass flow (i.e., volume of air flowing through the cooling device over a period of time), a compressor of the cooling device may need to provide a specific cooling capacity that corresponds to a compressor speed that is not one of the discrete operating speeds available to the compressor. Instead, the compressor may have to operate at a speed that is either too high and thus over-cools the electronic equipment or too low and thus under-cools the electronic equipment. Furthermore, the output temperature of a traditional cooling device having discrete compressor speeds may fluctuate as the compressor changes from one speed to another, especially if the steps between speeds are large.

As discussed above, even compressors that are variable between a minimum and maximum compressor speed are limited in operation to speeds above the minimum operating speed. This minimum operating speed corresponds to a minimum cooling capacity of a traditional cooling device. Between the minimum operating speed and a shutoff state, even these variable compressors are unable to provide a variable cooling capacity. As described above, this lack of variable cooling capacity may result in over-cooling, under-cooling, and/or temperature fluctuations.

In general, at least one embodiment of the invention is directed at providing more continuously variable cooling to an object being cooled with a cooling device by using supplemental heating. The object may include electronic equipment that may be damaged by improper cooling (e.g., over-cooling, under-cooling, cooling with a fluctuating temperature). In accordance with at least one embodiment of the invention, supplemental heating may provide more continuously variable cooling, by, for example, heating an air flow from a cooling device directed to the object to a temperature between the temperatures that might otherwise be generated by the cooling device operating at one of the limited available compressor speeds. It should be appreciated that when using the term “continuously variable” herein, the term should be read to include any variability that is more continuous than a cooling device's compressor operating alone would provide.

At least one embodiment of the invention is directed at a CRAC unit. Examples of CRAC units are disclosed in detail in U.S. patent application Ser. No. 11/335,874 filed Jan. 19, 2006 and entitled “COOLING SYSTEM AND METHOD,” Ser. No. 11/335,856 filed Jan. 19, 2006 and entitled “COOLING SYSTEM AND METHOD,” Ser. No. 11/335,901 filed Jan. 19, 2006 and entitled “COOLING SYSTEM AND METHOD,” Ser. No. 11/504,382 filed Aug. 15, 2006 entitled “METHOD AND APPARATUS FOR COOLING,” and Ser. No. 11/504,370 filed Aug. 15, 2006 and entitled “METHOD AND APPARATUS FOR COOLING” which are hereby incorporated herein by reference. One embodiment of a CRAC unit 101 is illustrated in FIG. 1. As shown, a rack 103 may be configured to house components of the CRAC unit 101.

Some implementations of the invention may include InRow RP Chilled Water Systems available from APC, Corp., West Kingston, R.I., Network AIR IR 20 KW Chilled Water Systems available from APC, Corp., West Kingston, R.I., FM CRAC Series Systems available from APC, Corp., West Kingston, R.I., and/or any other heating or precision cooling equipment.

In one embodiment of the invention, the CRAC unit 101 may include an evaporator 105 configured to cool air. The evaporator 105 may include multiple evaporator coils that may increase a surface area of the evaporator 105. A coolant may flow within the evaporator 105 (e.g., within the evaporator coils) in a liquid form. As air is drawn over the evaporator 105 (e.g., over or through the evaporator coils) the air may be cooled by the coolant. The coolant, conversely, may be warmed by the air as the air is drawn over or through the evaporator 105 thereby causing the coolant to evaporate within the evaporator coils.

In some embodiments of the invention, the air may be drawn across the evaporator 105 by one or more fans, each indicated at 107. The fans 107 may be arranged to draw warm air into the CRAC unit 101 from a direction indicated by arrows A, move the air passed the evaporator 105 so that the air is cooled, and then exhaust the cooled air from the CRAC unit 101 in a direction indicated by arrows B. Each fan 107 may be configured to adjust or otherwise vary a fan speed to increase or decrease the air mass flow of air drawn through the CRAC unit 101 and over the evaporator 105. As the fan speed increases, a larger air mass flow of air may be drawn through the CRAC unit 101. Conversely, as the fan speed decrease, a smaller air mass flow of air may be drawn through the CRAC unit 101. The fan speed may be controllable by a controller coupled to the CRAC unit 101, as described below.

It should be appreciated that in other implementations of a CRAC unit (e.g., 101) or other cooling device, fans (e.g., 107) may be replaced or supplemented with one or more other air and/or other fluid moving and/or directing devices. Air and/or other fluid moving and/or directing devices may be fully variable, semi-variable or non-variable. When the term “fan” is used herein it should be understood to include any air and/or other fluid moving and/or directing device, including fans, pipes, tubes, valves, directing surfaces, pumps, vents, etc. When the term “fan speed” is used herein, it should be understood to include any regulator of a mass flow of air or any other fluid being moved by any air and/or other fluid moving and/or directing device.

In one embodiment, the CRAC unit 101 may further include a condenser 109 configured to cool the coolant as cool air is drawn across the condenser 109. As shown, the condenser 109 may be an external device and may include multiple condenser coils that may increase a surface area of the condenser 109. The coolant may flow within the condenser 109 (e.g., within the condenser coils) in a gaseous form. As air is drawn over the condenser 109 (e.g., over or through the condenser coils) the coolant may be cooled by the air thereby causing the coolant to condense. As a result, the air may be warmed by the coolant and exhausted from the CRAC unit 101. In one embodiment, air may be drawn into the CRAC unit 101 through a plenum (not shown) along arrow C so as to move the air over the condenser 109 and along an air path defined by arrow D. Fans may be provided to achieve the air flow over the condenser 109 as described above. It should be understood that the condenser 109 may be provided within the CRAC unit 101.

In one embodiment, the flow of the coolant through and between the evaporator 105 and the condenser 109 may be facilitated by a compressor 111. The compressor 111 may pump coolant through pipes coupling the compressor 111 to the evaporator 105 and the condenser 109. The result is that coolant is warmed in the evaporator 105 as it cools air and the coolant is cooled in the condenser 109 as it warms air. The speed at which the compressor 111 pumps the coolant through the evaporator 105 may determine a cooling capacity of the evaporator 105 (i.e., amount of heat removed from the air over a period of time). If a greater volume of coolant per time is pumped to the evaporator 105, the evaporator 105 may produce a greater cooling capacity. If a lower volume of coolant per time is pumped to the evaporator 105, the evaporator 105 may produce a smaller cooling capacity.

In some implementations, a compressor (e.g., 111) may be fully variable between a minimum and maximum coolant flow rate. In other implementations, a compressor (e.g., 111) may be non-variable or semi-variable allowing one or a few discrete coolant flow rates. In still other implementations, a compressor (e.g., 111) may be configured as a matrix of multiple compressors that are each semi-variable, non-variable, or fully-variable between a minimum and maximum coolant flow rate. In some implementations, a compressor may be configured with a number of compressor cylinders and may operate using any number of the cylinders to provide a discretely variable output. In yet other implementations, a compressor may be configured with a hot gas bypass to provide some variable output. It should be appreciated that the invention is not limited to any specific compressor configuration listed above or otherwise. The flow rate of a compressor (e.g., 111) may be controlled by a controller coupled to the compressor, as described below.

In one embodiment, the CRAC unit 101 may include one or more sensors 113, each configured to measure one or more physical characteristics of the air flow through the CRAC unit 101. Measurements from the one or more sensors 113 may be used by a controller, as discussed below, to determine a desired cooling capacity of the CRAC unit 101. In one implementation, the sensors may include one or more of pressure, humidity, power consumption, and temperature sensors. The purpose of the sensors 113 will become apparent as the description of embodiments of the invention proceeds.

In accordance with one aspect of the invention, CRAC unit 101 may include one or more heating elements 115. FIG. 2 illustrates a schematic view of an example heating element 115 that may be used in one embodiment of the invention. In the heating element 115 of FIG. 2, a voltage may be applied across a plurality of heating coils, each indicated at 201. When the voltage is applied, the heating coils may dissipate heat. A fluid flow (e.g., air flow) directed along or near the heating coils may be warmed by that heat dissipated from the heating coils 201.

The invention is not limited to any specific type of heating element; rather, the heating elements may include any type of heat exchanger or heater, including an air-cooled heat exchanger, a plate heat exchanger, a gasket heat exchanger, a gas heater, an electric heater, a hot gas reheat system, a heating element that uses heated or superheated coolant to supply heat, a gas fired heater, etc. It should be appreciated that the heating elements may be any type or combination of types of heating elements that are capable of heating fluid (e.g., air) used to cool the electronic equipment.

In one embodiment, the heating element 115 may provide a heating output (i.e., amount of heat added to the air over a period of time) that is more variable than the cooling outputs available from the compressor 111. In one implementation, the heating element may provide a completely continuous heating output. In another implementation, the heating element may be variable between two available cooling outputs from the compressor 111. In yet another implementation, the heating element 115 may be capable of generating a pulsing heat output centered about a desired temperature generated, for example, by the heating element switching on and off repeatedly. In such implementations, the heating element may be configured to switch on and off at a higher rate than the compressor 111 capable of switching speeds (for example, because a compressor may only be capable of a limited number of cooling capacity adjustments in a given time period). In yet another implementation, the heating element may be capable of finer adjustments to heating capacity than the adjustments available to the cooling element, so that the combined output of the cooling element and heating element may be more variable than the cooling element operating alone.

In one embodiment, the heating element 115 may be disposed in the air flow through CRAC unit 101 such that the heating element 115 may heat the air going to the electronic equipment from CRAC unit 101. In one implementation, heating element 115 may be disposed between evaporator 105 and the electronic equipment. In another implementation, evaporator 105 may be disposed between the heating element 115 and the electronic equipment. In another embodiment, evaporator 105 may cool a first portion of the airflow and the heating element 115 may heat a second portion of the air flow. The first and second portion of the air flow may be combined to form the full air flow after the respective portions are heated and cooled. FIG. 3 illustrates a schematic view of a CRAC unit configured to divide an air flow into the first and second potions with a diverter 301, heat the first portion of the air flow with a heating element 303 and cool the second portion with a cooling element 305. The CRAC unit of FIG. 3 may then combine the first and second portions and output the combined air flow.

FIGS. 4A-4D illustrate some exemplary configurations of various CRAC units (e.g., 101) in accordance with various embodiments of the invention. As discussed, CRAC units (e.g., 101) are typically disposed in a data center room. FIG. 4A illustrates a room-based arrangement in which CRAC units 401, 403, 405, and 407 are disposed near the edge of a data center room and provide general cooling to the entire room, which is filled with rows of equipment racks, each row indicated at 409. FIG. 4B illustrates a rack-based arrangement in which a CRAC unit 411 is coupled to an equipment rack 413 to provide dedicated cooling to that specific equipment rack 413. FIG. 4C illustrates a row-based arrangement in which CRAC units each indicated at 415 are disposed or otherwise interspersed within rows of equipment racks, each equipment rack indicated at 417, to form hot aisles and cold aisles. The CRAC units 415 intake hot air exhausted by the equipment racks 417 from the hot aisles and output cold air to the cold aisles to cool the equipment racks 417. In such a configuration, equipment racks and CRAC units may be arranged in any ratio (e.g., two equipment units for every one CRAC unit, etc). FIG. 4D illustrates an alternative row-based arrangement in which CRAC units 419 and 421 are disposed along the ceiling of a data center room. The CRAC units 419 and 421 and the rows of equipment racks 423, 425, 427, and 429 of FIG. 4D form hot and cold aisles.

It should be appreciated that the above illustrations of the CRAC unit 101 in FIG. 1 and of CRAC unit configurations (e.g., FIGS. 4A-D) are given as examples only. Embodiments of the invention are not limited to any particular configuration of CRAC units or any particular CRAC unit. Furthermore, embodiments of the invention are not limited to CRAC units, but rather may include any cooling device configured to cool any object.

Furthermore, while the above descriptions may describe air-based cooling devices, it should be appreciated that the invention is not limited to air-based cooling devices. Rather, at least one embodiment of the invention may include any cooling device that provides cooling to any object by cooling any fluid. The fluid may include a gas and/or a liquid. Any reference to cooling devices or CRAC units should be understood to apply to any cooling devices using any fluid to cool any object.

FIG. 5 illustrates a block diagram of some components of a cooling device (e.g., a CRAC unit 101) according to at least one embodiment of the invention. As described in more detail below, FIG. 5 illustrates a controller 501, one or more controlled devices 505, 507, such as heating and cooling elements, and one or more sensors 509, 511, 513, 515 coupled by a communication network 503.

In one embodiment, the controller 501 may be dedicated to a single cooling device (e.g., CRAC unit 101). In another embodiment, the controller 501 may control a plurality of cooling devices (e.g., controller 501 may be part of a main data center control system or a dedicated cooling system). In one embodiment, the controller 501 may include a Philips XAG49 microprocessor, available commercially from the Phillips Electronics Corporation North America, New York, N.Y. The controller 501 may include a volatile memory and a static memory that may store information such as executable programs and other data useable by the controller 501. The controller 501 may be coupled to an external memory device, such as a hard disk drive (not shown) that may also store executable programs and other data usable by the controller 501. In various implementations, the controller 501 may include an analogue electric controller, a digital electric controller, a fluid or gas pressure logic device, and/or a mechanical logic device.

In one embodiment, the controller 501 may communicate with other components of the cooling device over a network 503. The network 503 may include an internal cooling device bus, a local area network, and/or a wide area network. The network 503 may include a wired portion (e.g., a portion including a mechanical connection between two points) and/or a wireless portion (e.g., a portion without a mechanical connection between two points, such as a Wi-Fi network).

As illustrated in FIG. 5, in one embodiment, the network 503 may couple the controller 501 to a cooling element 505 and a heating element 507. In one embodiment, the cooling element 505 may include a component of the cooling unit such as a compressor (e.g., 105) and/or a fan (e.g., 107), as described above. The controller 501 may communicate over the network 503 to adjust a parameter of the cooling element 505 such as a compressor speed and/or fan speeds. For example, the controller 501 may transmit a control signal to the cooling element 505 indicating a change in compressor speed; The cooling element 505 may receive the control signal from the network 503 and adjust the compressor speed accordingly. As another example, the controller 501 may transmit a control signal to the cooling element 505 indicating a change in fan speed. Cooling element 505 may receive the control signal from the network 503 and adjust the fan speed accordingly.

Substantially similarly, the controller 501 may communicate over the network 503 to adjust a parameter of the heating element 507. In one embodiment, the controller 501 may transmit a control signal to the heating element 507 indicating a change in heating output. The heating element 507 may receive the control signal and adjust the heating output accordingly. In one implementation, the heating element 507 may generate a constant heating output. In one implementation, the heating output of the heating element 507 may be controlled by adjusting a power level supplied to the heating element or a portion of the heating element. In one implementation the control signal may include an indication of the level of power to be supplied to the heating element 507 and the control signal may be transmitted to a power level controller of the heating element 507. In one implementation, the heating element 507 may generate a pulsing heat output that varies around a target heat output. In one embodiment, the controller 501 may transmit a pulse width modulated (PWM) control signal configured to operate the heating element 507 to provide a desired heating output. In one implementation, the percentage of high voltage time in the PWM signal may correspond with the amount of time in which the heating element 507 is generating heat. In one implementation, the high voltage time may be extended to increase the heating output and shortened to decrease the heating output.

In one embodiment, the controller 501 may execute one or more control loops (e.g., proportional-integral-derivative (PID) loops) written in a firmware of the controller 501 to determine when and which control signals should be transmitted to controlled devices (e.g., 505 and 507). The control signals may be transmitted to adjust one or more cooling parameter of the cooling element 505 and one or more heating parameters (e.g., power supplied to the heating element) of the heating element 507 so that a desired cooling output or other cooling condition may be maintained by the CRAC unit (e.g., 101). Such a desired condition may, for example, be entered by a user of the cooling device (e.g., a data center administrator) through a control panel coupled to the controller 501.

In one embodiment, the controller 501 may be configured to maintain a near constant air output temperature. As described below, in one aspect of the invention, it is recognized that the output air temperature of a cooling device may be adjusted by a heating element to provide more fully variable cooling. In general,

Cooling Provided=Output of Cooling Elements−Output of Heating Elements.  (1)

To be more accurate, additional heat produced by other elements of a cooling device may be accounted for, including heat produced by fans, heat produced by electronics of the cooling device, heat produced by a compressor, and/or heat produced by any other source.

For example, a cooling capacity of 1200 Watts may be required to cool the air flow passing through a cooling device to a desired temperature. The compressor speeds available to the cooling element 505 may provide only for cooling capacities of zero Watts, one thousand Watts and two thousand Watts. The desired cooling output of 1200 Watts may be generated by, for example, operating the compressor at the two thousand Watt level and heating the air with the heating element 507 by eight hundred Watts.

To that end, the controller 501 may determine the cooling capacity of the cooling element 505 and transmit a control signal to the cooling element 505 to increase the compressor speed as needed. The controller 501 may also determine the desired heating output of the heating element 507 and transmit a control signal to heating element 507 to adjust the heating output as needed.

To facilitate proper control of cooling parameters, some embodiments of the controller 501 and the network 503 may be coupled to one or more sensors 509, 511, 513, and 515. The sensors 509, 511, 513, and 515 may measure physical characteristics relevant to determining which control signals to send to controlled devices (e.g., 505, 507). The sensors 509, 511, 513, 515 may include temperature sensors 509, relative humidity sensors 511, pressure sensors 513, and/or any other sensors 515 that may measure any physical characteristic relevant to the control of a cooling device (e.g., absolute humidity, power consumption, etc.). In one embodiment, each of the sensors 509, 511, 513, 515 may communicate the measured physical characteristics to the controller 501 through the network 503. The measured physical characteristic may be communicated, in various implementations, by any method, including analogue electric, digital electric, pressure, mechanical, and any combination thereof. The controller 501 may then generate appropriate control signals based on the received information.

In one aspect of the invention, a cooling device (e.g., CRAC unit 101) may perform a process (e.g., 600) as illustrated in FIG. 6 so that the cooling device provides continuously variable cooling to an object. A set of graphs illustrating cooling output of cooling devices in operation according to some embodiments of the invention is shown in FIGS. 7A-D. The x-axis of graphs 701, 703, 705, and 707 of FIGS. 7A-D represent a desired cooling capacity. The y-axis of graphs 701, 703, 705, and 707 of FIGS. 7A-D represent a delivered cooling capacity.

Graph 701 of FIG. 7A illustrates the output of a cooling element (e.g., 505) having three states (off, one hundred percent cooling capacity, and fifty percent cooling capacity) and a heating element (e.g., 507) that is completely continuously variable, allowing a fully continuous combined output. Graph 703 of FIG. 7B illustrates the output of a cooling element having three states (off, one hundred percent cooling capacity, and fifty percent cooling capacity) and a heating element that is has five output states between each of the cooling element's output states, allowing a step-like continuous combined output. Graph 705 of FIG. 7C illustrates the output of a cooling element that is fully variable above an initial minimum output and a heating element that is completely continuously variable, allowing a fully continuous combined output even below the minimum output of the cooling element. Graph 707 of FIG. 7D illustrates an alternative operation of a cooling element that is fully variable over an initial minimum output and a heating element that is completely continuously variable, allowing a fully continuous combined output.

As indicated in block 601 of FIG. 6, in one embodiment, process 600 may begin with a cooling device (e.g., 101) determining a desired total cooling capacity (i.e., reduction in heat of air flowing through the cooling device over a period of time) based on a desired cooling condition and various sensor inputs. For example, a desired cooling capacity may be calculated by:

Q=Δt*m*k,  (2)

where Q is the desired cooling capacity, Δt is the desired difference in temperature between the intake air and air provided to the electronic equipment, m is the air mass flow of air moving through the cooling device (i.e., volume of air moving through the cooling device over a period of time), and k is the specific heat of air (e.g., 1,024 kJ/(kg*K)).

After determining the desired cooling capacity, a cooling device (e.g., CRAC unit 101) may adjust one or more cooling parameters (e.g., compressor speed) to generate a cooling capacity that is at least as great as the desired cooling capacity. As indicated in block 603, a controller (e.g., 501) may generate and transmit a control signal to change the cooling capacity of the cooling element so that a cooling element (e.g., 505) generates the new cooling capacity. Generated cooling capacities of cooling elements in accordance with at least one embodiment of the invention are illustrated by lines 709, 711, 713, and 715 of FIGS. 7A-D, respectively. As illustrated, the cooling capacities provided by the cooling elements alone may exceed the desired cooling capacity.

In one embodiment, the values of the one or more cooling parameters (e.g., compressor speed) may be determined, for example, based on a mapping of cooling parameter values to generated cooling capacities. Such a mapping may be generated and stored in a memory of the controller during the design and/or manufacturing process of the CRAC unit. In another embodiment, an equation may describe the relationship between the cooling parameters and the generated cooling capacity so that the cooling parameters may be determined from the equation using the desired cooling capacity as a variable value.

As indicated in block 605, in one embodiment, a cooling device (e.g., CRAC unit 101) may determine if the output cooling capacity of the cooling element exceeds the desired cooling capacity. If the output cooling capacity of the cooling element does not exceed the desired cooling capacity, but rather equals the desired cooling capacity, the cooling device may end process 600, or revert back to the beginning of process 600 to begin the process again.

However, if the cooling capacity of the cooling element alone is greater than the desired cooling capacity, the cooling device may operate a heating element (e.g., 507) to move the total cooling capacity of the cooling device towards the desired cooling capacity, as indicated in block 607. In one implementation, the desired heating output of the heating element may first be determined by:

Desired Heating Output=Cooling From Cooling Elements—Desired Cooling.  (3)

One implementation of operating a heating element comprising a plurality of heaters using pulse width modulated control signals is disclosed in is described in U.S. patent application Ser. No. ______ by Carlsen, et. al., filed Nov. 3, 2006, entitled “MODULATING ELECTRICAL REHEAT WITH CONTACTORS,” and having attorney docket number A2000-706119, and which is hereby incorporated herein by reference

In one embodiment, the cooling device may adjust the heating element to generate a heating output equal to or relatively close (e.g., to a level that when combined with the cooling capacity produced by the cooling element would bring the total cooling output of the cooling device closer to the total desired cooling output) to the desired heating output. In one embodiment, a controller (e.g., 501) may generate and transmit a control signal over a network (e.g., 503) to the heating element (e.g., 507) to adjust the heating output. In one implementation, the heating output of the heating element may be determined based on the power consumed by the heating element or a portion of the heating element:

Heating Output=V*I,  (4)

where V equals the voltage across the heating element and I equals the current flowing through the heating element. In such an implementation, the heating output of the heating element may be adjusted by varying one or more of the voltage and current supplied to the heating elements.

It should be recognized that the steps indicated by blocks 603, 605, 607 may be performed simultaneously or substantially simultaneously such that when the compressor speed is adjusted, the heating element is also adjusted simultaneously or substantially simultaneously. In addition, the initiation of process 600 may be configured to immediately restart after the prior process loop is completed.

The amount of heat output by a heating element is illustrated by lines 717, 719, 721, and 723 of FIGS. 7A-D, respectively. The cooling output of the CRAC units, determined, for example, by Equation 1 or some other equation accounting for the heating element output and cooling element output, is illustrated by lines 725, 727, 729, and 731 of FIGS. 7A-D, respectively.

As is illustrated in FIGS. 7A and 7C, the combined output 725, 729 of the heating element and the cooling elements may be such that the actual cooling output equals the desired cooling output of the cooling device for any desired cooling output if the heating element is fully continuously variable.

As illustrated in FIG. 7B, the combined output 727 of the heating element and the cooling element may be such the actual cooling output is generally closer to the desired cooling output than the cooling output of the cooling element operating alone. In the embodiment illustrated by FIG. 7B, the heating and cooling elements may be configured to operate together so that the combined output of the heating and cooling elements are closer to the desired cooling output than the configuration in which neither element is operated at all or the cooling element is operated alone. For example, below threshold cooling level 733 in FIG. 7B, the combined operation of the heating and cooling elements would produce the total output 735, which is farther away from the desired cooling output when neither the heating element nor cooling element is operated below that threshold. Above the threshold 733, however, one or both of the heating element and cooling element may be operated so that the combined output is as close to the desired output as available cooling and heating outputs allow.

As is illustrated in FIG. 7D, to reduce power consumption of the cooling and heating elements, in one embodiment of the invention, if minor cooling fluctuations or deficiencies may not adversely affect the cooled electronic equipment, the cooling device may not operate one or both of the cooling element and heating element when such operation could otherwise produce a desired total cooling output. For example, below the threshold value 737, because the electronic equipment may not be generating much heat and few if any adverse affects are possible at such a low heat level, neither the heating nor cooling elements may be operated, as illustrated in FIG. 7D. In one implementation, the threshold 737 may include five percent below the minimum cooling capacity of the cooling element alone. In one implementation, the threshold 737 may include a temperature difference from an ideal equipment temperature (e.g., five degrees Fahrenheit).

In another example, a similar principle may be applied at greater desired cooling capacities, such that the heating element may not operate until the desired cooling capacity differs from the actually delivered cooling capacity of the cooling element by some threshold amount. As illustrated in FIG. 7D, a cooling device may over-cool the electronic equipment until the difference between the desired cooling and actual cooling reaches a threshold value 739. Once the threshold value is reached, however, the heating device may begin to operate to reduce the difference between the desired cooling output and the actual cooling output of the cooling device, as described above. In one implementation, the threshold 739 may include five percent of the total possible output of the cooling device. In one implementation, the threshold 739 may include a temperature difference from an ideal equipment temperature (e.g., five degrees Fahrenheit).

It should be appreciated that process 600 and graphs 701, 703, 705, and 707 are described and illustrated as examples only. Any combination of heating and cooling output may be generated in accordance with at least one embodiment of the invention. Furthermore, any process may be performed to generate such heating and cooling output.

Although embodiments of the invention have been described with respect to electronic equipment in data center environments, it should be recognized that embodiments of the invention are not so limited. Rather, embodiments of the inventions may be used to provide cooling in any environment to any object or space. For example, embodiments of the invention may be used with telecommunication equipment in outdoor environments or shelters, telecommunication data centers, and/or mobile phone radio base-stations. Embodiments of the invention may be used to with precious goods such as art work, books, historic artifacts and documents, and/or excavated biological matters (for example, for preservation purposes). Embodiments of the invention may be used for preservation of meats, wines, spirits, foods, medicines, biological specimens and samples, and/or other organic substances. Further embodiments may be used for process optimization in biology, chemistry, greenhouse, and/or other agricultural environments. Still other embodiments may be used to protect against corrosion and/or oxidization of structures (for example, buildings, bridges, or large structures).

Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only. 

1. A method of providing variable cooling, the method comprising: A) operating a cooling element to cool an air flow by a first cooling capacity; B) operating a heating element to heat the air flow by a first heating capacity that adjusts the first cooling capacity towards a first desired total cooling capacity; C) determining a second desired total cooling capacity; D) controlling the cooling element to cool the air flow by a second cooling capacity that is greater than the second desired total cooling capacity; and E) controlling the heating element to heat the air flow by a second heating capacity that adjusts the second cooling capacity towards the second desired total cooling capacity.
 2. The method of claim 1, wherein the act A comprises cooling a first portion of the air flow, the act B comprises heating a second portion of the air flow, and the method further comprises an act of F) combining the first portion and second portion.
 3. The method of claim 1, further comprising an act of F) directing the air flow to at least one piece of electronic equipment.
 4. The method of claim 3, wherein the act F comprises directing the air flow to a data center room containing the at least one piece of electronic equipment is stored.
 5. The method of claim 3, wherein the act F comprises directing the air flow to an equipment rack containing the at least one piece of electronic equipment is stored.
 6. The method of claim 1, wherein the act D includes operating the cooling element at one of a set of discrete cooling capacities at which the cooling element is capable of operating.
 7. The method of claim 6, wherein the act E includes adjusting the one of the set of discrete cooling capacities by heating the air flow.
 8. The method of claim 6, wherein the cooling element includes at least one compressor having a set of discrete compressor speeds, and wherein the act D includes selecting one of the discrete compressor speeds.
 9. A cooling system comprising: a cooling element configured to cool a fluid flow by a variable cooling capacity to lower a temperature of the fluid flow; a heating element configured to heat the fluid flow by a variable heating capacity to raise the temperature of the fluid flow; and a controller configured to vary the cooling element and the heating element to generate a variable total cooling capacity corresponding to a combination of the variable cooling capacity and the variable heating capacity.
 10. The system of claim 9, wherein the cooling element is configured to cool a first portion of the fluid flow, the heating element is configured to heat a second portion of the fluid flow, and the system further comprises a discharge configured to combine the first portion and the second portion.
 11. The system of claim 9, wherein the cooling element includes at least one compressor configured to move a coolant through a cooling coil at a coolant flow rate that corresponds to a cooling capacity of the cooling element.
 12. The system of claim 11, wherein the compressor is configured to operate at one of a set of discrete coolant flow rates at which the at least one compressor is configured to operate.
 13. The system of claim 11, wherein the compressor is configured to operate at a coolant flow rate above a minimum coolant flow rate.
 14. The system of claim 11, wherein the at least one compressor includes a plurality of compressors.
 15. The system of claim 9, wherein the cooling system further comprises a discharge configured to direct the fluid flow to at least one piece of electronic equipment.
 16. The system of claim 15, wherein the discharge includes at least one fan.
 17. The system of claim 15, wherein the cooling element, heating element and discharge are part of a computer room air conditioning (CRAC) unit.
 18. The system of claim 9, wherein the heating element is disposed in the fluid flow between the cooling element and an object.
 19. The system of claim 9, wherein the cooling element is disposed in the fluid flow between the heating element and an object.
 20. A method of providing variable cooling, the method comprising: determining a desired total cooling capacity of an air flow; adjusting a cooling device to produce a variable cooling capacity to the air flow that is at least as great as the desired total cooling capacity; and in a first mode of operation, if the variable cooling capacity is greater than the desired total cooling capacity, adjusting a heating device to lower the variable cooling capacity towards the desired total cooling capacity.
 21. The method of claim 20, further comprising directing the air flow to at least one piece of electronic equipment.
 22. The method of claim 20, wherein adjusting a cooling device to provide the variable cooling capacity includes adjusting at least one compressor speed of the cooling device.
 23. The method of claim 20, wherein adjusting a heating device to lower the variable cooling capacity towards the desired total cooling capacity includes adjusting a power supplied to a heat exchanger of the heating device.
 24. The method of claim 20, wherein the desired total cooling capacity includes a cooling capacity that reduces a temperature of the air flow to a target temperature and the variable cooling capacity includes a cooling capacity that reduces the temperature of the air flow to a predetermined temperature that is lower than the target temperature.
 25. The method of claim 24, wherein the first mode of operation includes when the predetermined temperature differs from the target temperature by at least a threshold amount.
 26. The method of claim 25, wherein the threshold amount includes about five degrees Fahrenheit. 